Population centers in the U.S. and around the world will face increasing challenges to provide safe water supplies, and will increasingly demand new technologies for reclamation and reuse of wastewater.
Accordingly, supplies of safe drinking water will continue to be an important issue as science and techniques addressing water quality issues advance. The availability of technically and economically effective technologies for water treatment and reclamation is desirable. The presence of new contaminants of concern such as those identified by EPA's CCL 2 and effective methods for their control, therefore, is an important issue.
The removal of carbon, nitrogen, phosphorus, and micronutrients has become important to improving the quality of polluted water and restoring ecological balance. It is widely known that many aquatic plants absorb metals beyond their immediate needs, thus bio-concentrating them within plant cells as they remove them from water. Algae and other aquatic plants can take up primary and micronutrients that may be present in overabundance, such as carbon, nitrogen, phosphorus, potassium, iron, aluminum, calcium, and other substances and thus can be utilized to remediate an ecosystem.
The prior art teaches that there are many processes for bioremediation. One such natural process is when water flows over stationary algae or periphyton which, like all plants, require carbon. Periphyton has a higher productivity than any terrestrial plant. As modeled using the partial pressure of gas laws, this creates a significant consumption of carbon dioxide. Conservatively, 20 times more CO2 (in the form of bicarbonate) is absorbed by periphyton as is absorbed by a mature forest land on an equal area. Significantly higher cell productivity of periphyton greatly affects O2 production producing many times more O2 per unit area.
Water remediation by regularly harvested periphyton has been shown to be 50 to 1000 times higher than constructed wetland systems per unit area. Accordingly, remediation can occur when water flows over man-made or artificial stationary algae taking up macro nutrients (carbon, nitrogen and phosphorus) and micro nutrients, while discharging oxygen as high as three times saturation. Further, this high oxygen and hydroxyl environment can reduce organic sediments by 0.25 meters per year. In extended time experiments, periphyton increases pH due to carbon uptake to as high as 11. Filtration can occur through adsorption, absorption, physical trapping, and other more complex means.
Further studies of periphyton filtration are disclosed in U.S. Pat. Nos. 4,333,263; 5,131,820; 5,527,456; 5,573,669; 5,591,341; 5,846,423; and 5,985,147. Periphyton filters (PF) have found use in a variety of applications, for example, as filters in aquaria, natural periphyton are used to remove nutrients and other contaminants from polluted waters. However, such natural processes require large areas and consume vast resources and are impractical for large scale operation.
Other wastewater treatment techniques known in the art include the treatment of wastewater with ozone (triatomic oxygen or O3). Ozone is a naturally occurring gas created, for example, by the force of corona discharge during lightning storms or by UV light from the sun. Ozone occurs in an upper atmospheric layer and is believed to be critical to the temperature balance on Earth, while ozone in the lower atmosphere is commonly viewed as a pollutant. Ozone treatment is currently used for drinking and wastewater treatment as well as air filtration with doses taking into account health and safety factors. Examples of patents discussing the treatment of a sample with ozone include, among others, U.S. Pat. Nos. 7,014,767; 6,991,735; 6,394,329; 6,962,654; 6,921,476; 6,835,560; 6,780,331; and 6,726,885.
As well, it is known in the art to use microbubbles to treat a sample, such as a wastewater. Examples of the use of microbubbles to treat wastewater include generating microbubbles, coating them with a contaminant degenerative liquid, and passing the coated microbubbles through a wastewater stream. Other microbubble techniques include aeration of septic tanks by drawing atmospheric air into an expansion chamber and from there into agitated sludge to provide low pressure small microbubbles which have long residence times in the sludge material. Aeration devices which disperse microbubbles into a liquid and maintain transfer of gas to the liquid across a fiber membrane are also used where gas pressures are above the bubble point of the fiber membranes. A cloud of microbubbles is expelled into the liquid as it is forced to flow past the fibers. Although somewhat effective in decontamination, these approaches can be limited in their efficiencies, can require expensive equipment, and can be difficult to maintain.
Despite the above approaches and technologies, the need remains for methods and systems which can further increase treatment efficiencies and are safe, reliable and cost effective.